Emission on steel from laser cut
You can achieve this effect by using the dynamic paint system. Select your steel plate and give it a dynamic paint physics modifier, set it to be a canvas. Then set your laser object to be a dynamic paint brush. Add a wetmap output at the bottom of the canvas settings.
Now in your shader settings you can get a vertex info node and set import the wetmap data. Plug this into a principled BSDF in the emission strength settings and make sure to add a blackbody node into emission colour for the correct colour. Then just mess around with the spreading dissolving and shrinking paint effects until you get the look you want.

You can download an example of the effect I think you are going for with this blend exchange link.